1. Technical Field
The present disclosure relates to a battery detector for a portable electronic device, and more particularly, to a battery detector for detecting whether a battery module is coupled to a portable electronic device or not but without utilizing an internal resistor of the battery module.
2. Description of Related Art
Generally, portable electronic devices, such as a mobile phone or a personal digital assistant (PDA), need an external battery module for providing power to the portable electronic device. Except a positive terminal (+) and a negative terminal (−), a conventional battery module including the chargeable battery further comprises an identification (ID) terminal. In this configuration, an internal thermistor is coupled between the ID terminal and the negative terminal.
Taking a mobile phone as an example, when the battery module is coupled to the mobile phone, a control circuit of the mobile phone determines the battery module is coupled to the mobile phone according to a logical level detected at the ID terminal. If the control circuit detects that the ID terminal is at a logic low level, it is determined that the battery module is coupled to the mobile phone; On the contrary, if the control circuit is unable to detect that the ID terminal is at the logic low level, it is determined that the battery module is not coupled to the mobile phone.
Alternatively, the control circuit of the mobile phone can provide a control voltage to the ID terminal and obtains a corresponding current to calculate the resistance of the thermistor to further determine a temperature of the battery module. The control circuit of the mobile phone also determines whether the battery module is coupled to the mobile phone according to whether the corresponding current is generated.
Generally, manufacturer usually binds a transformer capable of providing matched direct current (DC) power to the mobile phone as accessory in a shipping package. When the mobile phone is not turned on yet and the transformer is plugged in the mobile phone for providing a DC power, the control circuit of the mobile phone conducts a startup procedure and determines whether the battery module is coupled to the mobile phone. After the electrical connection state between the mobile phone and the battery module is confirmed, a charger of the mobile phone is turned on for charging the battery module.
However, for the purpose of reducing cost, module manufactures no longer design the ID terminal in the battery module at present. Therefore, when the mobile phone receives the DC power provided from the transformer, the control circuit of the mobile phone cannot determine whether the battery module is coupled to the mobile phone. Thereby, erroneous operations happen in the startup procedure of the mobile phone.
For example, a liquid crystal display (LCD) panel of the mobile phone would be turned on during the startup procedure of the mobile phone. When power of the mobile phone is provided by the battery module or by the battery module together with the transformer at the same time, the mobile phone should get enough work current. Therefore, the LCD panel of the mobile phone is lightened and the startup procedure would be conducted smoothly.
On the contrary, when power of the mobile phone is provided by the transformer only, in the moment of lightening the LCD panel during the startup procedure, the entire mobile phone would be shut down if the charging current supplied by the transformer cannot support enough work current for the mobile phone. Therefore, the startup procedure would fail. After that, once the mobile phone is shut down, since the LCD panel no longer consumes power, the charging current supplied by the transformer is provided to the mobile phone again for conducting the startup procedure until the mobile phone is shut down once more when the LCD panel is lightened again. Accordingly, the LCD panel of the mobile phone presents repeatedly lightening and darkening behaviors in the view of user. Therefore, the panel is non-functional under such circumstance.
As mentioned above, if the mobile phone is not coupled to the battery module and only the DC voltage of the transformer is provided to the mobile phone, malfunctions may occur in the mobile phone when the control circuit of the mobile phone peremptorily starts the charger because the control circuit of the mobile phone cannot determine whether the battery module is connected to the mobile phone.